Testosterone is being prescribed to older men whose doctors simply don't have enough information to know if it can help or hurt them, says a doctor in a letter to The Lancet Diabetes and Endocrinology journal.

That could be placing men's health at risk, said Stephanie Page, an endocrinologist at the University of Washington.

Some smaller studies have revealed that testosterone treatment in older men is associated with increased cardiovascular risk. Others have not. (The benefits of testosterone therapy for younger men with a deficiency of the hormone is well established, she said.)

What's needed, she wrote, is a larger and longer study - whose results, unfortunately, wouldn't be final for at least a decade. Deciding that the smaller studies were sufficient "would do men's health a disservice," she wrote.

"Testosterone is a billion dollar industry, probably fueled partly by direct-to-consumer advertising and some degree or over-prescription," she said.